The invention relates to a seat belt retractor.
EP 0 842 831 B1 teaches a seat belt retractor frame, on which a two-piece belt reel is rotatably mounted. A seat belt is connected to the belt reel and can be wound onto or unwound from the belt reel. The seat belt retractor further comprises a tightening drive that generates a torque, which is transferred to the belt reel via a coupling. A load limiter connects the two reel parts to one another. The load limiter conveys a limited amount of the load exerted by the belt webbing on the seat belt-wearing vehicle occupant during an accelerated forward displacement of the vehicle occupant, in particular in a crash. Furthermore, in the known seat belt retractor, during efficient load limitation by a relative torsion of the two reel parts, the tightening drive is separated from the belt reel by disengaging the coupling.
There is provided in accordance with the present invention a seat belt retractor comprising: a two-piece belt reel rotatably mounted on a seat belt retractor frame, the belt reel comprising a spool onto which a seat belt webbing can be wound, said spool having a passageway extending longitudinally therethrough, and a spool insert inserted in said passageway; a tightening drive that generates a torque; a force transmission device via which torque can be transmitted from the tightening drive to the belt reel for winding up a webbing winding onto the spool; and a load limiter located in the passageway through said spool and connected to both the spool and the spool insert, said load limiter limiting force from a seat belt webbing on a seat belt-wearing vehicle occupant during an accelerated forward displacement of the seat belt-wearing vehicle occupant, whereby during the force limitation the spool insert is blocked against rotation and the spool rotates and energy is dissipated through the load limiter and the torque transmission from the tightening drive to the belt reel is interrupted, when a preselected force threshold resulting from the belt load limiter effect and the torque created by the tightening drive is reached in the force transmission device, the torque transmission from the tightening drive to the belt reel is stopped, whereby the restraint force upon the seat belt-wearing vehicle occupant originating from the applied seat belt is essentially determined by the load limiter alone.